Polyurethanes of differing types are produced by the polymerization of diisocyanates, for example 4,4′-methylenebis(phenyl isocyanate), MDI for short, or 2,4-tolylene diisocyanate, TDI for short, with polyether polyols or polyester polyols. Polyether polyols are obtainable, for example, by alkoxylation of polyhydroxy-functional starters. Examples of common starters are glycols, glycerol, trimethylolpropane, pentaerythritol, sorbitol or sucrose. Polyurethane foams are produced using additional blowing agents, for example, pentane, methylene chloride, acetone or carbon dioxide. It is customary to use surface-active substances, especially surfactants, to stabilize the polyurethane foam. In addition to a few organic based surfactants, silicone surfactants are typically used because of their higher interface stabilization potential.
A multiplicity of different polyurethane foams are known, examples include hot-cure flexible foam, cold-cure foam, ester foam, rigid PUR foam and rigid PIR foam. The stabilizers used have been specifically developed to match the particular end use, and typically give a distinctly altered performance if used in the production of other types of foam.
In the prior art, the polysiloxane-polyoxyalkylene copolymers used for polyurethane foam stabilization are generally produced by noble metal-catalyzed hydrosilylation of unsaturated polyoxyalkylenes with SiH-functional siloxanes, so-called hydrogen siloxanes, as described, for example, in EP 1 520 870. The hydrosilylation can be carried out batchwise or continuously, as described, for example, in DE 198 59 759 C1.
A multiplicity of further documents, such as, for example, EP 0 493 836 A1, U.S. Pat. No. 5,565,194 or EP 1 350 804, each disclose specifically assembled polysiloxane-polyoxyalkylene copolymers to achieve specific performance profiles for foam stabilizers in diverse polyurethane foam formulations.
In view of the fact that the availability of fossil resources, namely mineral oil, coal and gas, is limited in the long run and against the background of rising crude oil prices, there has been increased interest in recent years in using polyols based on renewable raw materials for producing polyurethane foams (see, WO 2005/033167 A2; U.S. Patent Application Publication No. 2006/0293400 A1). In the meantime, a whole series of these polyols has become available on the market from various producers (see, WO 2004/020497, U.S. Patent Application Publication No. 2006/0229375, or WO 2009/058367). Depending on the source of the raw material (e.g., soybean oil, palm oil or castor oil) and the subsequent processing steps, the polyols obtained differ in their property profiles. Essentially two groups can be distinguished:    a) polyols based on renewable raw materials which are modified such that they can be used at 100% for production of polyurethane foams (see WO 2004/020497, or U.S. Patent Application Publication No. 2006/0229375),    b) polyols based on renewable raw materials which, due to their processing and properties, can replace the petrochemically based polyol to only a certain extent (see WO 2009/058367, or U.S. Pat. No. 6,433,121).
The use of vegetable polyols of group B has distinct repercussions for the production of flexible polyurethane block foams, both for the process management and the physico-chemical properties of the resulting foam. For instance, the use of vegetable polyols produced from soybean oil or palm oil leads with increasing use level, under otherwise unchanged processing conditions, to a lengthening in rise time, a change in hardness and air permeability and also to reduced elongation at break, tensile strength and elasticity for the foam. Some changes, for example, rise time and air permeability, can be held in check by appropriately adapting the formulation, i.e., the catalyst combination. Other physical properties such as, for example, hardness, elongation at break, tensile strength and elasticity remain adversely changed.
U.S. Patent Application Publication No. 2010/0286295A1 and DE 102010039004 describe specific stabilizer structures for improving the physical properties of flexible polyurethane block foams from vegetable polyols. However, these stabilizers were specifically developed for the production of flexible polyurethane block foams from vegetable polyols. It is not advisable to use these stabilizers in conventional foam types, which do not contain any vegetable polyols. The result would be, for example, an excessive settling of the foam and a non-optimal density distribution within the foam block. However, customers prefer to use stabilizers that can be used for standard foams as well as flexible polyurethane slabstock foams from vegetable polyols.